This invention relates generally to an antenna and an antenna coupling device for radio equipment and more particularly relates to an antenna structure mounted in a movable housing element and coupled to a portable radio transceiver.
Antennas for portable radio equipment pose particular problems in the areas of efficiency and reliability. Preferably, an antenna should be of a size which is related to the wavelength of operation of the radio and should be located in a position away from conducting or absorbing materials. An externally exposed antenna which may meet these criteria, however, is subject to wear and abuse which shorten the antenna's lifetime.
It has been shown that an antenna could be placed in a location interior to the housing of a portable radiotelephone; for example see U.S. Pat. Nos. 5,014,346 and 5,170,173 assigned to the assignee of the present invention. The antennas disclosed therein are located in a housing flip element, thereby realizing separation of the antenna from the remainder of the housing and protection for the antenna radiating/receiving elements. Coupling to/from the antenna is realized by capacitive or inductive (transformer) coupling located in the knuckles of the hinge. Other techniques of coupling via a rotating joint have been to use flexible spring wiper elements or thin coaxial cables to bridge hinged elements. Either of these techniques suffer problems: coaxial cables are bulky, mechanically noisy, and prone to fatigue failure while contact-type connectors are electrically noisy and prone to wear. Fixed coupling to antennas through such media as glass, which has become popular for mounting cellular radiotelephone antennas to vehicular window glass, does not suffer the problems associated with movement of the coupling elements. The teachings of such fixed coupling techniques are of limited value for the embodiment of the present invention.
Placing an antenna in the radio housing or in a flip element may require compromises in the antenna configuration. Compensating for these compromises may require additional circuitry which consumes more physical volume in the portable radio. Thus, it would be desirable to include an antenna in a protective radio housing element while minimizing volume and number of elements in a device which couples the antenna to the radio.